Preheat the oven to 450 F. Arrange the onion slices at the bottom of a roasting pan.
Place warm water in a small bowl. Crush saffron threads between your fingers, add to the water, and set aside.
In a small bowl or liquid measuring cup, combine olive oil with the juice of lemons and clementines. Set aside lemon rinds, discarding clementine rinds.
Remove giblets and the neck from the chicken, rinse inside and out, and pat dry. Place the chicken breast on top of the onions.
Stuff the cavity with lemon rinds.
Truss the chicken if desired.
Drizzle the chicken with olive oil, massaging it over the skin. Sprinkle evenly with a pinch of kosher or sea salt, cinnamon, and cumin. Rub the spices over the skin.
Add saffron water to the oil and citrus juice mixture. Whisk to emulsify, and pour evenly over the chicken.
Roast the chicken at 450 F for 10 minutes.
Lower the temperature to 425 F. Continue roasting, occasionally basting, until cooked through (50 minutes to 1 hour and 20 minutes, depending on chicken size). When done, juices will run clear, the leg will wiggle freely, and a meat thermometer in the thigh will register 160 F/71 C.
Remove the chicken from the oven, allowing it to rest for 10 minutes before carving.